I was thinking from the website owner pov. However it would also be intriguing to look at it as a separate 'chapter' from the individual surfer's pov. That might give some further food for thought for the website owner. (customer-centric thinking and all that good stuff. )

An additional question on that subject might include: What do I do now, because of the search engines, which I might not have thought of otherwise?

Working with accessibility, machine-accessibility of the site data is a constant question; so many of the issues I deal with for search engines I would do regardless. However, I suspect I would never do anything with an xml sitemap, I probably wouldn't even think about robots.txt. Meta robots tags, similarly, would be out. I doubt that I'd spend much time on meta descriptions; but then, I also imagine that in a world without search engines meta data could become very important on some other levels...so maybe I would. Hard to say without a more detailed scenario.

I'm not sure I'd worry very much about whether or not pages were returning the right HTTP codes; although I'm sure I could come up with a reason that would still be important.

I would work a LOT harder at link building, though. Being completely dependent on links for traffic would make that aspect of web site ownership even more important.

On the whole, not a lot of what I do as a developer/designer would change, but the nature of site promotion would change radically.

Not a lot would change. The page content would be the same, the Title tag would be the same. No point in desription tag though (unless some directories used this for their own snippets of course)

In terms of getting links, I guess you would have to rely more on your own gut feeling an knowledge of your niche to find the sites that may send you the most traffic - rather than using this in conjunction with the sites place in the SERPs - but essentially you still have to get people linking to your site.

Presumably website designs can be much more visually attractive with lots of Flash. There's no need to have more text content than is visible to the human visitor. From that aspect, it would appear that some website designers are still living in that world and do not add anything 'behind the scenes' to help the search engine spiders. What you see is what is there.

Presumably website designs can be much more visually attractive with lots of Flash. There's no need to have more text content than is visible to the human visitor.

I'd disagree, on that point. Accessibility would still be just as important; just (at a guess) much less popular than it is now. As far as text visibility goes (or, more accurately, "content availability"), blind users would still be unable to use most Flash, the hard of hearing would still struggle with audio, requiring text alternatives, and keyboard users could still be unable to use mouse-dependent resources.

Right now, the world of SEO has, on the whole, made the web a much better and friendlier place for the disabled. So much of what SEOs do has spillover for accessibility that it's been a huge benefit. If those things were lost in a search-engine free world it would be a huge disaster.